The objective of this project are to investigate the influence of pregnancy on immune responses using in vitro mitogenci stimulation of pregnant women's peripheral blood T-and B-cells, and to examine the serum lymphocyte inhibitors during pregnancy. We noted that separation of lymphocytes by Ficoll-Hypaque gradient centrifugation results in higher degrees of tritiated thymidine (H3T) uptake by the lymphocytes cultured without mitogens in comparison with lymphocytes cultured without mitogens in comparison with lymphocyte cultures unseparated from polymorphonuclear cells (polymorphs). We have found that the high H3T uptake is due mostly to removal of polymorphs which have inhibitory effects on lymphocyte responses and, perhaps, partly due to lymphocyted stimulation by the Ficoll-Hypaque. We then isolated lymphocytes from preganant and non-pregnant control women, using cotton wool to remove the polymorphs. Cells from both groups of individuals demonstated a similar degree of responsiveness to fetuin, a calf fetal protein shown to stimulate human lymphocytes, when cultured in pooled normal human plasma. Investigation of the subpopulation of human lymphocyte stimulated by the fetuin suggested that depending on different lots of the fetuin, either B-cell or both B- and T-cells will be stimulated. Since minor components are detected in these fetuin preparations, further purification of the fetuin appears necessary in order to identify the pure B-cell or T-cell stimulant and to identify the exact nature o lymphocyte stimulating components in the fetuin preparations. The work is being carried out. BIBLIOGRAPHIC REFERENCE: Hsu, C.C.S., Comparative inhibitory effect of serum on lymphocyte responses to mitogenic stimulation. Internat. Arch. Allergy appl. Immunol., 50:14, 1976.